Post CU CMP polishing for reduced defects

Abstract

Cu metallization is treated to reduce defects and effect passivation, and to reduce leakage between lines, by removing surface defects subsequent to CMP and barrier layer removal. Embodiments include the sequential steps of: CMP and barrier layer removal; buffing with a solution comprising citric acid, ammonium hydroxide and deionized water to remove copper oxide; rinsing with deionized water or an inhibitor solution, e.g., benzotriazole or 5-methyl triazole in deionized water; buffing with an abrasive slurry; and rinsing with deionized water or an inhibitor solution.

What is claimed is:  
     
       1. A method of planarizing a surface containing copper (Cu) or a Cu alloy and reducing surface defects, wherein the wafer surface contains an interlayer dielectric having an upper surface and at least one opening; a barrier layer lining the opening and on the upper surface of the interlayer dielectric; and Cu or a Cu alloy filling the opening and on the barrier layer, the method comprising: 
       conducting chemical-mechanical polishing (CMP) to planarize the surface on a first platen to remove most of the Cu or Cu alloy layer leaving a film of Cu or Cu alloy on the barrier layer;  
       a first buffing on a second platen to remove the Cu or Cu alloy film and barrier layer leaving the Cu or Cu alloy layer in the opening with a exposed surface containing defects;  
       a second buffing with one of an abrasive slurry and a solution to remove copper oxide;  
       rinsing with an inhibitor solution following said second buffing;  
       a third buffing with another one of said abrasive slurry and said solution to remove copper oxide; and  
       rinsing with an inhibitor solution following said third buffing.  
     
     
       2. The method according to  claim 1 , wherein: 
       the solution capable of removing copper oxide comprises citric acid, ammonium hydroxide and deionized water; and  
       the inhibitor solution comprises benzotriazole or five-methyl triazole.  
     
     
       3. A method of planarizing a wafer surface containing copper (Cu) or a Cu alloy and reducing surface defects, wherein the wafer surface contains an interlayer dielectric having an upper surface and at least one opening; a barrier layer lining the opening and on the upper surface of the interlayer dielectric; and Cu or a Cu alloy filling the opening and on the barrier layer, the method comprising the sequential steps of: 
       (a) conducting chemical-mechanical polishing (CMP) to planarize the surface on a first platen to remove most of the Cu or Cu alloy layer leaving a film of Cu or Cu alloy on the barrier layer, and buffing on a second platen to remove the Cu or Cu alloy film and barrier layer leaving the Cu or Cu alloy layer in the opening with an exposed surface containing defects;  
       (b) buffing with a solution to remove copper oxide;  
       (c) rinsing with deionized water or an inhibitor solution;  
       (d) buffing with an abrasive slurry; and  
       (e) rinsing with deionized water or an inhibitor solution.  
     
     
       4. The method according to  claim 3 , wherein the solution employed in step (b) comprises citric acid, ammonium hydroxide and deionized water. 
     
     
       5. The method according to  claim 4 , wherein the inhibitor solution employed in step (c) and/or step (e) comprises benzotriazole or five-methyl triazole. 
     
     
       6. The method according to  claim 4 , wherein the solution employed in step (b) comprises about 2.0 wt. % to about 26 wt. % citric acid, about 0.020 wt. % to about 3.2 wt % ammonium hydroxide, the remainder deionized water. 
     
     
       7. The method according to  claim 6 , wherein the solution employed in step (b) comprises about 2.16 wt. % to about 25.9 wt. % citric acid and about 0.26 wt. % to about 3.1 wt. % ammonium hydroxide. 
     
     
       8. The method according to  claim 7 , wherein the solution employed in step (b) comprises about 8.63 wt. % citric acid and about 1.03 wt % ammonium hydroxide. 
     
     
       9. The method according to  claim 5 , wherein the inhibitor solution comprises about 0.01 wt. % to about 0.50 wt, % benzotriazole or 5-methyl-1-benzotriazole and deionized water. 
     
     
       10. The method according to  claim 4 , wherein the solution employed in step (b) comprises up to about 26 wt. % citric acid, up to about 5 wt. % ammonium hydroxide or an amine or up to about 5 wt. % of a combination of ammonium hydroxide and an amine, the remainder deionized water. 
     
     
       11. The method according to  claim 3 , comprising conducting steps (b) through (c) on a third platen. 
     
     
       12. The method according to  claim 4 , wherein the solution employed in step (b) has a pH of about 3.9 to about 4.1. 
     
     
       13. The method according to  claim 10 , wherein the solution employed in step (b) has a pH of about 3.9 to about 4.1.